The present invention relates to hand brake mechanism for setting the brakes of railway cars. Such hand brakes are used to manually apply the brakes on a railway car by pulling on a chain connected to the railway car brake rigging. This chain is connected to a rotatable drum of the hand brake mechanism. When a hand wheel is rotated, a gear mechanism interconnecting the hand wheel and the chain drum rotates the chain drum to cause the pulling force to be applied to the chain.
Perhaps the most commonly used of such gear mechanism consists of a plurality of spur gears. This enables the shaft of the hand wheel to be parallel to the shaft of the chain drum which is an advantageous arrangement. However, to maintain the car brakes in the locked position it is necessary that some sort of a locking mechanism, such as a ratchet, be employed. An example of such a brake mechanism will be seen in U.S. Pat. No. 3,353,902.
A gear drive between the hand wheel and the chain drum, which drive includes a worm and worm wheel, is advantageous since it eliminates the necessity for the ratchet mechanism. Hand brakes embodying such drives have been proposed; see for example U.S. Pat. No. 1,854,804. However, to the best of my knowledge these all have required that the hand wheel shaft be at right angles to the chain drum shaft. One feature of my invention is a gear drive arrangement which incorporates a worm and worm wheel, while at the same time maintaining the hand wheel shaft parallel to the chain drum shaft.
While the such hand brakes can be released by a reverse rotation of the hand wheel, it is conventional to include a release mechanism to permit disengagement of the chain drum for free rotation to achieve release of the railway car brakes. Due to the tensioning provided by the brake rigging and the weight of the chain, the reverse rotation of the chain drum, which occurs when the release mechanism is so disengaged, results in a rapid reverse rotation of the drum. To prevent the inertia of the drum from causing a reverse winding of the chain on the drum, a stop often is employed. When this stop is encountered during such release of the chain drum, the inertia results in a substantial impact. It is desirable to retard the rotation of the chain drum when the brake is released through disengagement of the release mechanism, so that the chain and drum do not develop such a rapid rotation. Brakes to retard the rotation of the chain drum upon release of the release mechanism have been proposed. See U.S. Pat. No. 3,979,969.
The herein disclosed embodiments incorporate brakes to retard the rotation of the chain drums when the release mechanisms are released. As compared to such brakes heretofore proposed, the herein disclosed brakes are advantageous in that they are simple in construction requiring a minimum of parts. Furthermore, they are extremely sturdy and reliable to withstand the forces applied thereto, necessary to retard the chain drum rotation, without significant deterioration over years of use. In the present invention, such brakes comprise an annular brake drum with a peripheral braking surface against which a brake shoe is urged by the mechanism utilized to release the release mechanism. The brake shoe is restrained against all but a radial movement toward and away from the brake drum surface. The shoes are cammed toward the surface, with the interposition of a spring, as the release lever is actuated.
Further objects and advantages will become apparent from the following description and the accompanying drawings.